Conventionally, a technique called MIP (Mobile Internet Protocol) is used to provide mobile terminals with mobility. In the MIP technique, an anchor router called an HA (Home Agent) manages a correspondence relationship (binding information) between an IP address used by an MN (Mobile Node; mobile terminal) for communication, which will be hereinafter referred to as HoA (Home Address), and an IP address belonging to a network (terminal herein as “visited network”) in which the MN exists, which will be hereinafter referred to as CoA (Care-of Address). When the HA receives an IP packet sent to the HoA of a destined MN, the HA encapsulates the IP packet and forwards the encapsulated IP packet to the CoA of the MN. In this way, the MN can receive the packet. Since the HA updates the binding information concerning the MN as the MN moves, the MN registers the location thereof to the HA regularly or every time the MN moves.
However, in recent years, in view of provision of mobility to terminals that do not support MIP or effective utilization of the radio frequency band resources, a technique called PMIP (Proxy MIP) in which the MN function in MIP is switched from a mobile terminal to an access network is being developed (see Non-Patent Document 1, for example).
Mobility management of a mobile terminal according to a conventional MIP, which will be hereinafter referred to as CMIP (Client MIP) to differentiate it from PMIP, will be described with reference to FIG. 8. An HA 12 manages mobility of a mobile terminal 3 using CMIP, irrespective of an access network connected by the mobile terminal 3. In FIG. 8, a mobile network 105 comprises: the HA 12; a AAA server 14; cellular networks 121 and 122; and WiMAX networks 131 and 132. The cellular networks 121 and 122 and the WiMAX networks 131 and 132 comprise routers 251 to 254. In FIG. 8, the mobile terminal 3 captures a CoA having a prefix included in a router advertisement advertised by the router 253 by means of DHCPv6, Stateless Address Auto Configuration, or the like, and the mobile terminal 3 then registers a correspondence relationship between the CoA and the HoA thereof to the HA 12 on its own.
However, in the mobility management based on such conventional CMIP, in view of provision of mobility to terminals that do not support CMIP or effective utilization of the radio frequency band resources, a technique called PMIP in which the MN function in CMIP is switched from a mobile terminal to an access network is being developed.
CMIP and PMIP have advantages and disadvantages regarding function deployment, security model of access network, effective utilization of resources, and the like. Thus, one idea for efficient mobility management is to selectively use two kinds of protocols (CMIP and PMIP) depending on the capability of the access network and manage mobility of each mobile terminal with a single HA. In this case, it is assumed that the HA also has the LMA (Local Mobility Anchor) function, which is the HA for PMIP.    Non-Patent Document 1: S. Gundavelli, et al., “Proxy Mobile IPv6” (IETF.draft-sgundave-mipv6-proxymipv6-01. Jan. 5.2007)